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Exercise for Weight Loss: The Best Approach for Optimal Results

Undoubtedly, we are in the midst of a well - known global obesity epidemic.

I. Unveiling Human Body Fat

The storage and consumption of fat is a dynamic process. The energy obtained from the diet is stored in fat cells in the form of triacylglycerols. This storage mechanism is similar to saving money for future needs. However, over time, this form of storage may also lead to an excess of fat, resulting in overweight and obesity. By interfering with this mechanism through various means to reduce fat storage, weight loss can be achieved.

Fat typically accounts for about 20% of a man's body weight and 28% of a woman's. In obese individuals, adipose tissue can expand several times, accounting for more than 80% of body weight [6]. The turnover rate of mature fat cells (i.e., the rate of cell renewal) is approximately 0.2% - 0.3% per day, equivalent to a half - life of about 300 - 400 days. Although there is turnover, the total number of fat cells seems to remain relatively stable throughout adulthood [7, 8]. Therefore, when losing weight, we not only aim to reduce the quantity of fat but also need to shrink its volume.

Interestingly, fat in different parts of the body has different impacts on health. Research shows that the accumulation of upper - body adipose tissue (abdominal obesity, also known as visceral fat) increases the risk of metabolic diseases and all - cause mortality, while the accumulation of lower - body fat (obesity in the buttocks and thighs) is beneficial to health [9, 10]. This means that the goal of weight loss is not only to reduce fat but, more importantly, to eliminate the fat that is harmful to health.

II. The Big Difference Between Exercising and Not Exercising

It is easy to see that when the breakdown (consumption) of stored fat exceeds storage, creating an energy deficit, weight loss can be achieved.

The total daily energy expenditure (TEE) of the human body is shown in the following table. It mainly includes basal metabolic rate (BMR), thermic effect of food (TEF, referring to the additional energy expenditure caused by eating), non - exercise activity thermogenesis (NEAT, referring to the energy consumed by the human body in daily activities such as standing, walking, and even being nervous), and exercise - associated thermogenesis (EAT, referring to the energy consciously consumed through exercise) [11].

The energy consumed by physical activity (including NEAT and EAT) is the most variable component of total energy expenditure. In extreme cases, a sedentary person's energy consumption from physical activity may be only a few hundred kilocalories per day (about 10% - 20% of TEE), while a very active person can consume several thousand kilocalories per day through physical activity (about 60% - 70% of TEE) [12]. This means that exercise is the most effective way to create an energy deficit.

Currently, it is generally believed that when the energy deficit reaches 500 calories, effective fat reduction will be initiated [13]. Exercise can also bring many health benefits (including a reduction in the risk of various diseases and all - cause mortality), which cannot be obtained by simply reducing the same amount of body fat through liposuction.

III. How Does Exercise Help with Weight Loss?

Research has found that exercise has an impact on the quantity, distribution, and quality of fat [14 - 17].

The energy deficit caused by increased physical activity leads to a loss in the quantity of adipose tissue, manifested as a reduction in subcutaneous fat, a smaller waist circumference, and a lower BMI [16, 17]. This reduction in quantity is because exercise stimulates blood flow in adipose tissue and activates fat mobilization, causing fatty acids to transfer from adipose tissue to tissues such as skeletal muscle, reducing the storage of dietary fat.

It is worth noting that when the intensity and duration of exercise vary, the effects on fat in different parts also differ. Therefore, the impact of exercise on visceral fat has received particular attention. After all, as the notorious "bad" fat, even methods like liposuction cannot solve the problem of visceral fat.

Currently, it is believed that when the exercise intensity reaches 10 MET - hours per week [MET stands for Metabolic Equivalent of Task, where 1 MET is the resting metabolic rate, i.e., the energy consumed by the body at rest; for a person weighing 90 kilograms, 10 MET - hours per week is equivalent to about 950 kilocalories per week], there will be a significant reduction in visceral fat [19]. Researchers speculate that this may be because when the intensity is ≥ 10 MET - hours per week, the sympathetic nerves are effectively activated, and visceral adipose tissue is more sensitive to adrenaline activation, thus benefiting from it. This also means that choosing the right exercise intensity can specifically reduce the amount of visceral fat that is harmful to health.

In addition to affecting the quantity of fat, exercise also has an effect on fat volume. This is very important because during the process of weight gain, the first change in fat cells is that they become larger, and the number only increases when the amount of fat increases significantly.

Research has found that exercise can transform large - volume fat cells into smaller, more metabolically flexible fat cells [20]. Regardless of BMI, large - volume fat cells are harmful to health, while small - volume fat cells have a protective effect on the body (having a positive impact on diastolic blood pressure, total cholesterol, LDL cholesterol, and insulin sensitivity). Changing fat volume is also a unique effect of exercise that cannot be achieved through dieting [21, 22].

The above are the body changes after a single exercise. If you exercise regularly, long - term exercise will bring physiological changes to adipose tissue, increasing fat oxidation at rest. That is, even without energy deficiency, fat oxidation still increases, achieving long - term fat reduction.

Moreover, even a low - level of exercise, if persisted in for a long time, may activate the body's "fat - burning switch," amplifying the lipolytic response of all subsequent physical activities [12, 23]. This means that exercising regularly in the morning can "amplify" the exercise effect throughout the day, resulting in significant benefits.

IV. Different Types of Exercise Have Different Effects

There are many types of exercise. So, what kind of exercise can effectively reduce fat? Is standing at work or doing housework enough? Or do you have to lift weights or run?

After all, the definition and scope of exercise are very broad. In a broad sense, exercise refers to any skeletal muscle movement with higher energy consumption than at rest (ranging from standing still, which is about 0.2 - 0.3 kilocalories per minute higher than the resting state, to high - speed sprinting, which is more than 20 kilocalories per minute higher than the resting state). In a narrow sense, exercise refers to planned workouts [24].

When evaluating the fat - reducing effect of exercise, a commonly used classification method is to divide exercise according to different intensities. The so - called exercise intensity refers to the energy cost per minute during exercise. Among them, exercises with a metabolic rate 3 - 6 times higher than the resting state are collectively referred to as moderate - intensity exercises [25]. Those higher than 6 times are high - intensity exercises, and those lower than 3 times are low - intensity exercises.

Whole - body measurements show that fat oxidation increases significantly after low - intensity exercise and further increases when the intensity reaches about 60% - 65% of the maximum oxygen uptake (V̇O2max, referring to the maximum amount of oxygen the body can utilize during exercise) [26, 27]. 60% - 65% V̇O2max is equivalent to moderate - intensity exercise, corresponding to a heart rate range of 55% - 69% of the maximum heart rate (about 100 - 150 beats per minute). Measurements of abdominal fat also confirm this finding. Low - intensity exercise can significantly increase fatty acid mobilization [28 - 30]. As the exercise intensity continues to increase (beyond 65% V̇O2max), fat will be transferred to other storage sites (such as other fat areas or intramuscular fat). During high - intensity exercise, fatty acid mobilization in adipose tissue is actually inhibited. In summary, fat oxidation during exercise reaches its maximum at about 60% - 65% V̇O2max [31].

Brisk walking, jogging (6 - 8 kilometers per hour), cycling (12 - 16 kilometers per hour), mountain climbing, stair - climbing, swimming, etc. all belong to moderate - intensity exercises. Physically, when doing moderate - intensity exercises, your breathing and heart rate increase slightly, you don't breathe heavily, you break a light sweat, you feel a little tired, but you won't feel fatigued when you wake up the next day.

Research has found that performing the above - mentioned moderate - intensity exercises for more than 250 minutes per week can lead to a clinically significant weight loss (more than 5%) [32 - 35]. However, these benefits will be lost if you stop exercising.

V. What if You Don't Like to Exercise or Don't Have Time to Exercise?

It's not that we don't know the benefits of exercise, but it's difficult to set aside a large block of time for exercise and to stick with it. According to data from the National Health and Nutrition Examination Survey (NHANES), 36.1% of people are basically sedentary, and another 47.6% have a low level of physical activity [36]. Most people exercise with sufficient intensity for no more than 2 hours per week, accounting for only 1% - 2% of the total daily energy expenditure on average [37].

So, it seems quite difficult to lose weight through exercise.

Don't be discouraged. Let's recall the table in part 2. In the energy consumption of physical activity, in addition to exercise - associated thermogenesis, there is also NEAT (non - exercise activity thermogenesis). In daily life, the energy consumed in maintaining body posture (such as standing or sitting), walking, climbing stairs, typing, playing the piano, singing, cooking, vacuuming, cleaning windows, etc. all fall into the category of NEAT.

For example, for an ordinary person who sits for most of the time, simply changing from sitting to standing can increase daily NEAT by about 700 kilocalories [38]. Doing housework by yourself, including buying groceries, cooking, cleaning dishes, and tidying up the room, may result in a NEAT difference of about 1000 kilocalories compared to ordering takeout and lying on the couch to watch mobile phones after work [39]. Increasing walking and reducing the use of vehicles and elevators can increase NEAT by 29% [40]. In addition, getting enough sleep also seems to help increase NEAT, as people tend to be more sedentary when they don't get enough sleep [41].

These activities are very common in daily life and not difficult to carry out. Although the effects are not as obvious as those of exercise, they can add up over time, resulting in weight loss that can be maintained in the long term [42].

VI. How to Exercise for the Best Weight - Loss Results

Research has found that exercising at different times of the day yields different results [43, 44]. Exercising in the morning (before 11 a.m.) has a more obvious weight - loss effect and is easier to stick with [45]. It is speculated that this may be related to the influence of the circadian rhythm. In addition, after each exercise, blood flow in adipose tissue increases for several hours, and the secretion of various fat - related factors (IL - 6, MCP - 1, MIP - 1α, TNF - α, leptin, etc.) also changes, enhancing fat oxidation during other physical activities after morning exercise [18].

Although the fat oxidation rate is higher on an empty stomach, research has found that exercising on an empty stomach can increase the activity of lipoprotein lipase (LPL) in adipose tissue, leading to more fat storage [46, 47]. Exercising on an empty stomach not only requires concern about low blood sugar but may also significantly reduce the fat - reducing effect of exercise.

The World Health Organization (WHO) recommends [48] that adults (18 - 64 years old) and the elderly (over 65 years old) should engage in at least 150 - 300 minutes of moderate - intensity aerobic activities or at least 75 - 150 minutes of vigorous - intensity aerobic activities per week. Adults should also perform muscle - strengthening activities of moderate or higher intensity, targeting all major muscle groups, at least 2 days a week.

For children and adolescents, it is recommended that they engage in an average of 60 minutes of moderate - intensity aerobic activities per day, mainly aerobic exercises. They should also have at least 3 days a week of vigorous - intensity aerobic exercises and activities that strengthen muscles and bones.

When exercising, it is necessary to avoid sports injuries. For people who don't exercise for a long time, their muscles may gradually atrophy, muscle strength will decline, and stability will also deteriorate. This is because mitochondria, as important organelles regulating the metabolic state of skeletal muscle, experience mitochondrial network disorders and mitochondrial function impairment after long - term disuse [49]. Therefore, it is recommended to follow the FITT principle [a basic principle for scientific exercise and improving health, named after the initials of Frequency, Intensity, Time, and Type] when exercising, and gradually carry out safe and effective workouts.

The fat - reducing effect of a single physical exercise is usually limited because the energy deficit may be compensated for through other channels such as diet. Long - term training is needed to increase the sensitivity of adipose tissue to hormones such as norepinephrine and insulin, and to increase total energy expenditure and fat oxidation. Even in daily physical activities, long - term accumulation can cause moderate changes in fat oxidation and significantly increase the daily fat oxidation amount [18].

Research has found that lack of sleep can stimulate appetite - regulating hormones, increasing the craving for carbohydrates and junk food. By extending sleep time, for example, sleeping 1.2 hours more per day, energy intake can be reduced by 270 kilocalories [51]. At the same time, poor sleep can also affect the basal metabolic rate (BMR). Although the change in its value is not large, if it persists for a long time, it can still have a non - negligible impact, leading to muscle atrophy, reducing exercise endurance and intensity, not only greatly reducing the exercise effect but also increasing the risk of sports injuries.

Research indicates that doing housework 5 times a week for half an hour each time can not only achieve the weight - loss effect of exercise and fitness but also reduce the mortality rate by 28% [52]. The Dietary Guidelines for Americans state that housework such as sweeping, mopping, and vacuuming is equivalent in intensity to walking at a moderate speed (5 kilometers per hour) [53]. For example, for a 50 - kilogram woman engaging in 30 minutes of activity, washing dishes and ironing clothes can consume 47 kilocalories; walking the dog can consume about 80 kilocalories; cooking can consume 86 kilocalories; cleaning the bathroom, mopping, and sweeping can consume about 91 kilocalories; and doing laundry can consume 105 kilocalories. For most people, doing housework is much easier than exercising to consume the same amount of energy.

VII. What if You Exercise but Don't Lose Weight?

We've talked a lot about the benefits of exercise, but there's an unavoidable problem - some people exercise a lot but still don't lose weight.

This may be due to the body's own total energy expenditure constraint mechanism [54]. That is, when you first start increasing your exercise volume, it will indeed lead to a significant change in energy consumption. However, as time passes, even if you maintain the same exercise volume or increase it, the body will actively reduce the energy consumed in other parts to keep the total energy expenditure at a relatively stable level. This mechanism evolved to ensure human survival, aiming to prevent excessive exercise from affecting health or endangering life.

However, this doesn't mean that exercise is ineffective. Don't give up because of this. In this case, you can adjust your diet on the basis of exercise, limit calorie intake, and take both approaches simultaneously. This can not only help you lose weight but also bring a series of health benefits (reducing the risk of various diseases such as diabetes and cancer).

So, what are you waiting for? Let's get moving!